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AP: Must Pay Attention in Stop and Go Traffic

Yeah, I know, you MUST pay attention to what's in front of at all times when using AP, but I just wanted to point out that AP currently does not handle a relatively common traffic pattern in stop and go traffic.

Twice now, when a freeway lane beside me has been blocked off (both times for accidents in those lanes), a car beside me merges quickly and closely into my lane - this is the typical cars alternating and merging at slow speed when a lane ends. AP does NOT see a quickly merging car coming into your lane. AP continues to try to keep distance from the original car ahead in your lane, oblivious to the merging car until it is too late.

The first time this happened to me, I was not paying attention, and my car's collision warning sounded, and I just barely had time to stomp on the brakes, missing the new car's bumper by inches.

The second time, I was ready and expecting this behavior, so I had time to watch what was happening. When cars are merging from a lane that is closing, they expect the car behind them to give them room to merge, so they leave very little room for the merge. According to the AP display, AP does not see the newly merging car until it is at least halfway into your lane. Since the AP does not see the merging car, it continues to drive towards the car that used to be in front of it, which can result in an accident if the driver does not take control away from AP (by stepping on the brake).

After seeing this behavior again today, I paid attention to cars coming up from behind me at a slow relative speed in lanes beside me. The AP display would not show these cars until they were at least two car lengths ahead of my car. Needless to say, this lack of immediately sensing new cars beside you coming up from your rear, is what causes this dangerous situation when travelling slowly, since there are situations were cars will essentially and legitimately cut you off.

I was using distance control of 4, Model X. I still love my AP and love to use it. However, I will now be expecting to take over when cars are merging into my lane in stop and go traffic (as well as other cases I've discovered of course).

Mods - can we have an Autopilot forum topic all by itself? These AP discussion are generic to both the Model X and S (and soon Model 3), so there should be some logical place to put such discussions rather than in the model specific forums.

I learned this lesson my first 5 minutes using autopilot. Even using distance setting of 1 is not enough in LA. People will merge/cut in front of you. I get around this by speeding up slightly and encouraging merging vehicles to merge behind me.

dial up the following distance and it works fine to allow merging cars in front of you when that is intended. I actively dial up and down the following distance when on full autopilot for exactly these reasons. you have to put the kindle down to do it though. perhaps that is the problem.

Yes I have seen that behavior where where a car slides into your lane and S doesn't slow down until it is well inside your lane by several inches. Interestingly the graphic clearly shows the dynamic position of that car and you can see that it detects how far it is inside your lane quite accurately, but still TACC would not react to it.

This is a problem only in slow moving stop and go traffic, where sometimes the car that is sliding in lingers in that position for much longer.

Yeah, I know, you MUST pay attention to what's in front of at all times when using AP, but I just wanted to point out that AP currently does not handle a relatively common traffic pattern in stop and go traffic.

Twice now, when a freeway lane beside me has been blocked off (both times for accidents in those lanes), a car beside me merges quickly and closely into my lane - this is the typical cars alternating and merging at slow speed when a lane ends. AP does NOT see a quickly merging car coming into your lane. AP continues to try to keep distance from the original car ahead in your lane, oblivious to the merging car until it is too late.

The first time this happened to me, I was not paying attention, and my car's collision warning sounded, and I just barely had time to stomp on the brakes, missing the new car's bumper by inches.

The second time, I was ready and expecting this behavior, so I had time to watch what was happening. When cars are merging from a lane that is closing, they expect the car behind them to give them room to merge, so they leave very little room for the merge. According to the AP display, AP does not see the newly merging car until it is at least halfway into your lane. Since the AP does not see the merging car, it continues to drive towards the car that used to be in front of it, which can result in an accident if the driver does not take control away from AP (by stepping on the brake).

After seeing this behavior again today, I paid attention to cars coming up from behind me at a slow relative speed in lanes beside me. The AP display would not show these cars until they were at least two car lengths ahead of my car. Needless to say, this lack of immediately sensing new cars beside you coming up from your rear, is what causes this dangerous situation when travelling slowly, since there are situations were cars will essentially and legitimately cut you off.

I was using distance control of 4, Model X. I still love my AP and love to use it. However, I will now be expecting to take over when cars are merging into my lane in stop and go traffic (as well as other cases I've discovered of course).

Mods - can we have an Autopilot forum topic all by itself? These AP discussion are generic to both the Model X and S (and soon Model 3), so there should be some logical place to put such discussions rather than in the model specific forums.

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I spend a lot of time (intentionally) in the carpool lane so I can't get cut off from the left and you are less likely to get cut off from the right in LA the way the HOV lanes are marked. That said I usually have my follow distance set to 5 car lengths which seems to lessen the situation you mentioned. But when I don't want to get cut off in heavy traffic I dial it down to 1.

Also in heavy traffic you may want to lower your cruise control speed to around 30 mph (or less) to prevent sudden acceleration when a gap appears. But I've found 5 car length setting and a lower cruse speed to work well in bumper to bumper traffic, give it a try and let us know.

Yes 5 works great. Remember that number is definitely not car lengths or seconds either. It is just a relative number that will maintain more distance at higher numbers. More at higher speeds and less at lower speeds.

Twice now, when a freeway lane beside me has been blocked off (both times for accidents in those lanes), a car beside me merges quickly and closely into my lane - this is the typical cars alternating and merging at slow speed when a lane ends. AP does NOT see a quickly merging car coming into your lane. AP continues to try to keep distance from the original car ahead in your lane, oblivious to the merging car until it is too late.

Click to expand...

Very odd. I recently completed a trip that included passing thru downtown Vancouver and downtown San Francisco, both during rush hour. Never had that experience.

I was not using AP, just TACC, so maybe my experience is not comparable to yours. I also admit that the merging SOB, er vehicle, was at least halfway into my lane before TACC slowed. But it always worked flawlessly -- to the point where I confess to becoming somewhat complacent. So I imagine @bhzmark is pointing his criticism at me.

It depends on your follow distance (set at 4, 5, 6, etc.), speed you are travelling at, how fast the person merges, and distance the person cutting in front leaves. My point is, don't be complacent.

If the other lane is closing, the person will cut in front of you very close to your bumper, making the assumption that you will slow down to give him room. Since TACC/AP doesn't see him until he is halfway across your lane, this can result in an accident unless you take over.

We have not taken delivery of our Model S yet, but we had one for a sleep over last week. The owners manual says TACC uses the camera and the radar for data. I noticed in the loaner that cars in the adjacent lane did not show till somewhat forward of our location. It appears to me that the radar and the camera scan a pie shaped sector in front of the car for traffic. If my assumption is correct, as a car passes you, it would not display until it entered that cone, either by driving far enough ahead, or by coming in laterally. I think the original post on the thread doesn't have to do with speed, but with position. It is just that people seldom cut in so closely unless the traffic is moving quite slowly.

I agree that the bottom line is ALWAYS PAY ATTENTION, even when driving slowly.

As this photo from Tesla shows the camera (blue) and radar (green) can NOT detect the car to the left of the Tesla, although the parking sensors can (yellow) the car to the right is out of parking sensor range yet is detected by the camera and radar. It's good to know the limits of the hardware. That said, although this is an "official" Tesla photo, no legend was ever included with the picture.

I ran into this (figuratively...) not long after I got the car, back before we had autosteer. Someone cut in front like this and my car got way too close to it before I stopped it myself. Since then I've been more careful.

That said, I'm not entirely sure it would actually collide with the car that cuts in. It clearly will get too close for comfort, but it may stop before actually making contact. Not that I'm going to test it to destruction.

Complacent is not the same thing as inattentive. Complacent, in this case, means I didn't have a death grip on the steering wheel, my foot wasn't hovering over the brake pedal, and my pulse wasn't racing. I've come to trust TACC much more than I ever thought I would.

I keep it at 7 here in Seattle. I have a high degree of confidence in Autopilot in traffic, with easily 15,000 miles of autopilot on I-5 clocked. Sometimes I find myself zoning out listening to music and wondering how I got to my exit so fast, and have to merge over pretty quickly.

I know you can't do this in other cities without getting honked at for leaving a gap, but I've never had issues merging with AP at seven. Theres enough room for any car to get in there without rear ending them. I am more worried anytime I am going over 60 mph, as sometimes it doesn't keep in the lane as good as it should through a curve.

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